Turbo compressor and refrigerator with the compressor

ABSTRACT

A turbo-type compressor having an improved performance which may be produced without increasing its size or cost, and the performance of a refrigeration unit is also improved when it is provided with such a turbo-type compressor.  
     The turbo-type compressor includes a casing ( 55 ) provided with an intake opening and a discharge opening; a rotation shaft ( 41 ) operated by a driving mechanism; an impeller ( 19 ) provided integrally with the rotation shaft ( 41 ); a diffuser section ( 46 ) constituted by a pair of a first wall section ( 56 ) and a second wall section ( 58 ), located at the outer periphery side of the impeller ( 19 ) to serve as a fluid passage for a refrigerant driven towards the outer side by the rotation action of the impeller ( 19 ). The refrigerant is drawn in through the intake opening, by the action of the impeller ( 19 ) which is rotated together with the rotation shaft ( 41 ) and driven by a motor, to be compressed and discharged through the outlet opening. In this compressor, the diffuser section ( 46 ) is constructed in such a way that the width dimension in the axial direction of the outlet opening ( 46   b ) is made larger than the width dimension of the inlet opening ( 46   a ).

TECHNICAL FIELD

[0001] The present invention relates to a turbo-type compressor used forcompressing liquids by a rotating impeller, and relates to arefrigeration apparatus having the compressor.

BACKGROUND ART

[0002] Conventionally, a turbo-type compressor is used in refrigerationapparatuses as a means of compressing refrigerant. The turbo-typecompressor compresses a fluid by rotating a rotation shaft provided withan impeller.

[0003] The structure of a conventional turbo-type compressor will beexplained with reference to FIG. 10.

[0004] As shown in the figure, an impeller 3 having a plurality of vanes2 arranged in a circumferential direction with spaces therebetween isattached to a rotation shaft 1 of the turbo-type compressor so that thevanes can be rotated with the rotation shaft 1. A rotor constituted bythe rotation shaft 1 and the impeller 3 is housed inside a casing 4.

[0005] The interior of the casing 4 is divided by a partition plate 5into a diffuser section 6 and a return passage 7, and the diffusersection 6 and the return passage 7 are communicated with a return bendsection 8 having U-shaped cross section.

[0006] The diffuser section 6 is constituted by a first wall section 4 aon the casing side and a second wall section 5 a on the partition plateside, and the first wall section 4 a and the second wall section 5 a areoriented perpendicular to the rotation shaft 1 while being parallel toeach other. Also, a plurality of return vanes 9 are spacedcircumferentially so as to guide the flowing fluid.

[0007] In this turbo-type compressor, the fluid compressed by theimpeller 3 and output to the diffuser section 6 is forwarded to thereturn passage 7 through the return bend section 8.

[0008] In such a compressor, the diffuser section 6 comprised by thefirst wall section 4 a and the second wall section 5 a serves todecelerate the flow of the fluid driven by the impeller 3 and recoversmost of the dynamic pressure as static pressure, and the pressurerecovery coefficient Cp, which is a parameter to indicate theperformance of the turbo-type compressor, is influenced by the shape ofthe diffuser section 6.

[0009] Therefore, the pressure recovery coefficient Cp may be increasedby improving the area and shape of the inlet opening 6 a and outletopening 6 b of the diffuser section 6.

[0010] However, in a conventional compressor, as shown in the graph inFIG. 11, the pressure recovery coefficient Cp has not reached a value of0.5, thus leaving room for further improvement. For this reason, thereare demands to improve the performance of the turbo-type compressor bymodifying the pressure recovery coefficient Cp in the diffuser section6.

[0011] Here, the pressure recovery coefficient Cp is expressed by theaspect ratio and the area ratio of the inlet and outlet openings 6 a and6 b of the diffuser section 6.

[0012] The aspect ratio and the area ratio are obtained according to thefollowing expressions:

Aspect ratio is given by 2ΔR/b2=2(R2−R1)/b2  (1)

Area ratio is given by AR−1=(R2b2/R1b1)−1  (2)

[0013] where

[0014] R1 is a radius at the inlet opening 6 a of the diffuser section6;

[0015] R2 is a radius at the outlet opening 6 b of the diffuser section6;

[0016] b1 is a width dimension of the inlet opening 6 a of the diffusersection 6; and

[0017] b2 is a width dimension of the outlet opening 6 b of the diffusersection 6.

[0018] Also, the pressure recovery coefficient Cp for the diffusersection 6 is represented by the following expression:

pressure recovery coefficient Cp=(Ps2−Ps1)/(Pt1−Ps1)

[0019] where

[0020] Ps1 is a static pressure at the inlet opening 6 a of the diffusersection 6;

[0021] Ps2 is a static pressure at the outlet opening 6 b of thediffuser section 6; and

[0022] Pt1 is a total pressure at the inlet opening 6 a of the diffusersection 6.

[0023] It can be seen that the level of recovery of the dynamic pressureinto static pressure of the fluid, which is compressed and output by theimpeller 3, can be improved by an amount corresponding to an increase inthe pressure recovery coefficient Cp.

[0024] The present invention takes into consideration theabove-mentioned circumstances, and objects thereof include providing ahigh efficiency turbo-type compressor having improved performancewithout increasing the size of the compressor, and providing arefrigeration apparatus including such a turbo-type compressor.

DISCLOSURE OF INVENTION

[0025] In order to achieve the above objects, the present inventionprovides a turbo-type compressor comprising a casing provided with anintake opening and a discharge opening; a rotation shaft operated by adriving mechanism; an impeller provided integrally with the rotationshaft; a diffuser section formed by a pair of wall sections at outerperipheries of the impeller to serve as a fluid passage for a fluiddriven towards the outer periphery side by the rotation of the impellerso that the fluid is drawn in from the inlet opening, by the action ofthe impeller which is rotated together with the rotation shaft anddriven by the driving mechanism, to be compressed and discharged fromthe discharge opening through the diffuser section; wherein the diffusersection is formed in such a way that the width dimension in the axialdirection of an outlet opening located at the outer periphery side ismade larger than the width dimension of an inlet opening for the fluidwhich is driven by the impeller.

[0026] Accordingly, because the width dimensions of the openings in theaxial direction of the inlet side and the outlet side are made so thatthe outlet side is larger relative to the inlet side, the aspect ratioof the inlet side and the outlet side is made somewhat smaller and thearea ratio is made larger, so that the pressure recovery coefficient inthe diffuser section can be made larger. This design enables effectiverecovery of the dynamic pressure of the compressed fluid output from theimpeller into a static pressure in the diffuser section without makingthe structure larger or more complex, and accordingly, a highcompression efficiency is realized in the turbo-type compressor of thepresent invention.

[0027] In another aspect of the invention, in the turbo-type compressordescribed above, the width dimension of the outlet opening is madelarger than the width dimension of the inlet opening without alteringthe area ratio of the inlet opening to the outlet opening of thediffuser section.

[0028] Accordingly, without altering the area ratio of the inlet openingto the outlet opening in the diffuser section, the width dimension ofthe outlet opening is made larger relative to the width dimension of theinlet opening. That is, because the radius of the outlet opening isreduced by an amount corresponding to the increase in the widthdimension of the outlet opening, the outer radius can be made smallerand the cost of the compressor can be reduced.

[0029] Also, even if the area ratio of the inlet opening to the outletopening is not altered, because the width dimension of the outletopening is made larger relative to that of the inlet opening, the aspectratio is reduced, and the pressure recovery coefficient is made largerso as to reliably improve the performance.

[0030] In yet another aspect of the invention, in the turbo-typecompressor described above, the pair of wall sections forming thediffuser section is tapered so as to separate gradually from each otherfrom the inlet opening towards the outlet opening.

[0031] That is, by tapering the pair of wall sections forming thediffuser section, the performance of the compressor is readily improvedby enlarging the width dimension of the outlet opening relative to thatof the inlet opening. Also, because the wall sections are tapered, it ispossible to avoid the problem of stream separation in the diffusersection of the refrigerant output from the impeller.

[0032] In yet another aspect of the invention, in the turbo-typecompressor described above, one of the wall sections forming thediffuser section is formed into a tapered shape so as to separategradually from the other one of the pair of wall sections from the inletopening towards the outlet opening.

[0033] In other words, by making only one of the wall sections thatconstitute the diffuser section, into a tapered shape, the performanceof the compressor can be improved quite readily by increasing the widthdimension of the outlet opening relative to the inlet opening. Also,because only one of the wall sections needs to be made into a taperedshape, the performance can be improved even more easily.

[0034] In particular, by tapering the wall section in the front sidewhich has more space as compared with the rear side of the impellerhaving a downstream side passage that communicates with the diffusersection, the dimension in the axial direction can be made smaller.

[0035] In yet another aspect of the invention, in the turbo-typecompressor described above, the compressor is a multi-stage compressorhaving a plurality of the impellers and compresses the fluid from theintake opening sequentially by using, first, an upstream-side impellerfirst, and successive impellers afterward.

[0036] In other words, the present multi-stage impeller provides asuperior turbo-type compressor of high performance because the pressurerecovery coefficient is improved in each stage of compression byrespective impellers at the respective diffuser sections serving as thefluid path for the fluid output by the respective impellers.

[0037] The refrigeration apparatus according to the present inventionincludes a compressor for compressing a refrigerant admitted from aninlet opening and discharging the refrigerant from a discharge opening;a condenser for condensing and liquefying the refrigerant and forwardinga liquefied refrigerant; a throttling mechanism for reducing thepressure of the liquefied refrigerant; a vaporizer for cooling an objectto be cooled by exchanging heat between the object to be cooled and aresultant condensed and pressure-reduced liquefied refrigerant, andevaporating and vaporizing the liquefied refrigerant, wherein thecompressor is a turbo-type compressor described above.

[0038] In the present refrigeration apparatus, because a high efficiencyturbo-type compressor, having a diffuser section that exhibits highperformance and produces a high recovery coefficient, is used as acompressor to compress the refrigerant and to output the compressedrefrigerant to the condenser, the cooling efficiency can be improvedsignificantly, and accordingly, the refrigeration apparatus can producesuperior cooling performance.

BRIEF DESCRIPTION OF DRAWINGS

[0039]FIG. 1 is a perspective view to explain the structure andconstruction of a turbo-type compressor in an embodiment of the presentinvention and a refrigeration apparatus having the compressor.

[0040]FIG. 2 is a schematic diagram to explain the structure of theturbo-type compressor and the refrigeration apparatus having thecompressor in the embodiment of the present invention.

[0041]FIG. 3 is a cross sectional view of the turbo-type compressor toexplain the construction of the turbo-type compressor according to theembodiment of the present invention.

[0042]FIG. 4 is a cross sectional view of a compression section toexplain the construction of the turbo-type compressor according to thepresent invention.

[0043]FIG. 5 is a graph showing the performance of a diffuser section ofthe turbo-type compressor according to the embodiment of the presentinvention.

[0044]FIG. 6 is a cross sectional view of the compression section toexplain the construction of a turbo-type compressor according to anotherembodiment of the present invention.

[0045]FIG. 7 is a graph showing the performance of the diffuser sectionof the turbo-type compressor according to the another embodiment of thepresent invention.

[0046]FIG. 8 is a cross sectional view to explain the construction ofthe turbo-type compressor according to yet another embodiment of thepresent invention.

[0047]FIG. 9 is a cross sectional view of the compression section of theturbo-type compressor according to still another embodiment of thepresent invention.

[0048]FIG. 10 is a cross sectional view to explain the construction of aconventional turbo-type compressor.

[0049]FIG. 11 is a graph showing the pressure recovery coefficient atthe diffuser section.

BEST MODE FOR CARRYING OUT THE INVENTION

[0050] A turbo-type compressor and a refrigeration apparatus providedwith the turbo-type compressor according to an embodiment of the presentinvention will be described with reference to the attached drawings.

[0051] An overall structure of the refrigeration apparatus will beexplained first with reference to FIGS. 1 and 2.

[0052] The refrigeration apparatus shown in the figures includes avaporizer 11 for cooling the cold water by means of heat exchangebetween the refrigerant and the cold water and for evaporating andvaporizing the refrigerant; a compressor 12 for compressing therefrigerant vaporized in the vaporizer 11; a condenser 13 for condensingand liquefying the refrigerant compressed in the compressor 12; athrottle valve 14 for reducing the pressure of the refrigerant liquefiedin the condenser 13; an intermediate cooler 15 for temporarily storingand cooling the refrigerant liquefied in the condenser 13; and an oilcooler 16 for cooling the lubricating oil for the compressor 12 byutilizing a portion of the refrigerant cooled in the condenser 13.

[0053] Also, a motor (a driving mechanism) 17 is connected to thecompressor 12 for operating the compressor 12.

[0054] The vaporizer 11, the compressor 12, the condenser 13, thethrottle valve 14 and the intermediate cooler 15 are connected via aprimary piping 18 to constitute a closed system in which the refrigerantis circulated.

[0055] The compressor 12 is based on a 2-stage (multistage) centrifugalcompressor, a so-called turbo compressor, and this turbo compressor 12is provided with a plurality of impellers 19. The refrigerant iscompressed in a first stage impeller 19 a situated in the upstream sideof the impeller 19, and the compressed refrigerant is led into thesecond stage impeller 19 b to be compressed further and is then sent tothe condenser 13.

[0056] The condenser 13 includes a main condenser 13 a and a sub-cooler13 b which is an auxiliary compressor, and the refrigerant is introducedfirst to the main condenser 13 a and then to the sub-cooler 13 b.However, a portion of the refrigerant cooled in the main condenser 13 ais introduced into the oil cooler 16, without passing through thesub-cooler 13 b, to cool the lubricating oil.

[0057] Also, apart from the above process, a portion of the refrigerantcooled in the main condenser 13 a is introduced into the casing 31 ofthe motor 17, which will be explained later, without passing through thesub-cooler 13 b, and cools stators and coils which are not shown in thediagram.

[0058] The throttle valve 14 is disposed between the condenser 13 andthe intermediate cooler 15, and between the intermediate cooler 15 andthe vaporizer 11, and they are used for stepwise reduction of thepressure of the refrigerant liquefied in the condenser 13.

[0059] The structure of the intermediate cooler 15 is equivalent to ahollow vessel, and the refrigerant which has been cooled in the maincondenser 13 a and the sub-cooler 13 b and reduced in pressure in thethrottle valve 14, is temporarily stored therein and is subjected tofurther cooling. Here, the vapor phase components in the intermediatecooler 15 are introduced into the second stage impeller 19 b of thecompressor 12 through the bypass piping 23, without passing through thevaporizer 11.

[0060] The turbo-type compressor 12 provided for the above-mentionedrefrigeration apparatus will be further explained in detail below.

[0061] As shown in FIG. 3, the motor 17 is provided integrally with theturbo-type compressor 12, which is operated by the rotational drivingpower of the motor 17.

[0062] The rotational power of the rotation shaft 35 of the motor 17 istransmitted to the rotation shaft 41 which constitutes the turbo-typecompressor 12 by means of engaged transmission gears 36 and 37, therebyoperating the rotation shaft 41 of the turbo-type compressor 12.

[0063] The turbo-type compressor 12 is designed so that one end sidethereof is designated as the intake opening 42, and the refrigerant fromthe vaporizer 11 is thereby output to the intake opening 42. Intakevanes 40 are disposed at the intake opening 42 so that the intake vanes40 control the intake volume of the refrigerant at the intake opening42.

[0064] The turbo-type compressor 12 is provided with a first stagecompression section 43, and a second stage compression section 44, inthat order, from the intake opening 42 side, and provided on the firststage compression section 43 and the second stage compression section 44are the first stage impeller 19 a and the second stage impeller 19 bdescribed above.

[0065] Then, by rotating the rotation shaft 41, the first stage impeller19 a and the second stage impeller 19 b are respectively rotated, andthe refrigerant from the vaporizer 11 is withdrawn into the first stagecompression section 43 from the intake opening 42, compressed by thefirst stage impeller 19 a of the first stage compression section 43,output to the second compression section 44 via the return passage 49which includes the diffuser section 46, return bend section 47 and thereturn vane 48, and is compressed by the second impeller 19 b of thesecond compression section 44. After that, the refrigerant passesthrough the diffuser section 46 and is discharged from the dischargeopening 53 via the scroll section 52, which is a fluid passage formed inthe circumference direction, to be sent to the condenser 13.

[0066] As described above, the refrigerant sent from the intermediatecooler 15 is output to the second stage compression section 44, and iscompressed together with the refrigerant output from the first stagecompression section 43 by the second stage impeller 19 b of the secondstage compression section 44. Then, the refrigerant, as described above,passes through the diffuser section 46 and is discharged from thedischarge opening 53 via the scroll section 52, to be sent to thecondenser 13.

[0067] Next, the structure of the diffuser section 46 in the first stagecompression section 43 and the second compression section 44 will beexplained by using the structure of the diffuser section 46 in the firststage compression section 43 as an example.

[0068] As shown in FIG. 4, in the diffuser section 46, the first wallsection 56 that includes the casing 55 of the turbo-type compressor 12,and the second wall section 58 that includes the partition plate 57 areformed in such a way to separate from each other in the radialdirection, and in so doing, the diffuser section 46 is formed in atapered shape so as to widen gradually from the inlet opening 46 atowards the outlet opening 46 b, with the result that the widthdimension of the diffuser section 46 in the axial direction becomesgradually wider towards the outer radial direction.

[0069] As described above, the turbo-type compressor 12 is formed insuch a way that, in the diffuser section 46, the width dimension b2 ofthe outlet opening 46 b is wider than the width dimension b1 of theinlet opening 46 a (b1<b2), and therefore, the aspect ratio of the inletopening 46 a and the outlet opening 46 b of the diffuser section 46 issomewhat reduced and the area ratio of the inlet opening 46 a to theoutlet opening 46 b of the diffuser section 46 is increased.

[0070] By adopting such a design, as shown in FIG. 5, in the case of theturbo-type compressor 12 having the diffuser section 46, the pressurerecovery coefficient Cp is increased to a point located at the left andabove the 0.5 value which is higher than the Cp exhibited by theconventional turbo-type compressor having the diffuser section 6 inwhich the width dimension of the inlet opening 46 a is the same as thatof the outlet opening 46 b, and therefore, the performance of thediffuser section 46 is enhanced and the efficiency of the turbo-typecompressor 12 is improved.

[0071] Similarly, the pressure recovery coefficient Cp is also improvedin the diffuser section 46 of the second stage compression section 44.

[0072] Note that although only a two-stage (multi-stage type) turbo-typecompressor having the first stage impeller 19 a and the second stageimpeller 19 b is explained above, it is obvious that the presentinvention may be applied to a singe-stage turbo-type compressor havingone impeller.

[0073] As explained above, according to the turbo-type compressor 12having the structure described above, because the width dimensions inthe axial direction at the inlet opening 46 a side and the outletopening 46 b side of the diffuser section 46 are made in such a way thatthe width of the outlet opening 46 b side is larger than that of theinlet opening 46 a side, the aspect ratio at the inlet opening 46 a sideand the outlet opening 46 b side is made somewhat smaller and the arearatio thereof is made larger, so that it is possible to increase thepressure recovery coefficient Cp at the diffuser section 46.

[0074] In other words, without making the structure complex, it becomespossible to efficiently recover a dynamic pressure of the compressedrefrigerant, which is output from the first stage impeller 19 a and thesecond stage impeller 19 b, in the form of a static pressure in thediffuser section 46, and accordingly, the turbo-type compressor 12having a superior compression efficiency may be realized without makingthe apparatus larger or more complex.

[0075] Also, the tapered shape of the pair of wall sections, comprisedby the first wall section 56 and the second wall section 58, whichconstitute the diffuser section 46, readily enables improvement in theperformance by enlarging the width dimension of the outlet openingrelative to that of the inlet opening. Also, because the first wallsection 56 and the second wall section 58 are tapered, it is possible toeliminate a problem of separation of the refrigerant in the diffusersection 46, which is output from the first stage impeller 19 a and thesecond stage impeller 19 b.

[0076] Also, since the turbo-type compressor 12 described above is atwo-stage type (multi-stage type) having the first stage impeller 19 aand the second stage impeller 19 b, and the pressure recoverycoefficient Cp is made larger at the diffuser section 46, which is thepassage for the refrigerant output from the first stage impeller 19 aand the second stage impeller 19 b, an extremely high efficiencyturbo-type compressor may be realized, in which the efficiency has beenincreased in the first stage impeller 19 a as well as in the secondstage impeller 19 b.

[0077] According to the refrigeration apparatus having the turbo-typecompressor 12 explained above, because the highly efficient turbo-typecompressor 12 having the diffuser section 46, which exhibits a superiorperformance in terms of the high pressure recovery coefficient Cp, isused, it becomes possible to significantly increase the coolingefficiency to provide a refrigeration apparatus having superior coolingcharacteristics.

[0078] Next, other embodiments according to the invention will beexplained.

[0079] As shown in FIG. 6, in the case of this diffuser section 46 also,the first wall section 56 comprised by the casing 55 of the turbo-typecompressor 12 and the second wall section 58 comprised by the partitionplate 56 are disposed in such a way to separate from each other towardsthe outer radial direction to form a tapered diffuser section 46 thatwidens from the inlet opening 46 a towards the outlet opening 46 b, sothat the width dimension of the diffuser section 46 gradually becomeswider towards the outer radial direction.

[0080] However, in this diffuser section 46, by making the radius R2smaller at the outlet opening 46 b, the area ratio of the inlet opening46 a to the outlet opening 46 b is kept the same as the area ratio priorto the improvement.

[0081] In other words, the area ratio is left unchanged in thisturbo-type compressor 12 while the aspect ratio is reduced, andtherefore, in the case of the turbo-type compressor 12 having thediffuser section 46, the pressure recovery coefficient Cp shifts, asshown in FIG. 7, to the left so as to be above 0.5 as compared with theCp of a conventional turbo-type compressor having a conventionaldiffuser section, thereby improving the performance of the diffusersection 46 and increasing the efficiency of the turbo-type compressor12.

[0082] Accordingly, in the case of the turbo-type compressor 12 havingthe above-mentioned structure, because the width dimensions in the axialdirection are such that the outlet opening 46 b side is made largerrelative to the inlet opening 46 a side without altering the area ratioof the inlet opening 46 a side to the outlet opening 46 b side in thediffuser section 46, the aspect ratio of the inlet opening 46 a side andthe outlet opening 46 b side is reduced so that the pressure recoverycoefficient Cp in the diffuser section 46 can be made larger.

[0083] In other words, without making the structure complex, it ispossible to efficiently recover a dynamic pressure of the refrigerant,which is output from the first stage impeller 19 a and the second stageimpeller 19 b, in the form of a static pressure in the diffuser section46, and accordingly, the turbo-type compressor 12 may have a superiorcompression efficiency without making the apparatus larger or morecomplex.

[0084] Further, without altering the area ratio of the inlet opening 46a to the outlet opening 46 b in the diffuser section 46, the widthdimension b2 of the outlet opening 46 b is made larger relative to thewidth dimension b1 of the inlet opening 46 a, that is, because theradius R2 of the outlet opening 46 b is reduced by an amountcorresponding to the increase in the width dimension b2 of the outletopening 46 b, the outer radius can be made smaller and the cost of thecompressor can be reduced.

[0085] Also, because the width dimension b2 of the outlet opening 46 bis made larger relative to that of the inlet opening 46 a withoutaltering the area ratio of the inlet opening 46 a to the outlet opening46 b, it becomes possible to assuredly improve the performance of thecompressor 12 by reducing the aspect ratio and increasing the pressurerecovery coefficient Cp.

[0086] Note that although a tapered diffuser section 46 that widens fromthe inlet opening 46 a towards the outlet opening 46 b, and the widthdimension of the diffuser section 46 which gradually becomes widertowards the outer radial direction are formed by separating the firstwall section 56, which includes the casing 55 of the turbo-typecompressor 12, away from the second wall section 58, which includes thepartition plate 57 towards the outer radial direction, in all of theabove embodiments, the efficiency of the turbo-type compressor 12 can beincreased by increasing the pressure recovery coefficient Cp so long asthe width dimension of the outlet opening 46 b side is made wider thanthat of the inlet opening 46 a side to an extent that would not cause aseparation of fluid stream in the diffuser section 46.

[0087] Here, in the embodiment shown in FIG. 8, only the second wallsection 58, which includes the partition plate 57, is inclined to form atapered shape, and in the embodiment shown in FIG. 9, only the firstwall 56, which includes the casing 55, is inclined to form a taperedshape. In either case, the degree of tapering is restricted so as not tocause a stream separation in the diffuser section 46.

[0088] According to the diffuser section 46 shown in FIG. 8 or 9, one ofthe wall sections, i.e., either the first wall section 56 or the secondwall section 58, is tapered and the other wall section is oriented atsubstantially right angles to the rotation axis 41, so that thestructure of the compressor may be simplified and the cost thereof maybe reduced as compared with the case where both of the first wallsection 56 and the second wall section 58 are tapered.

[0089] Here, when the second wall section 58 comprised by the partitionplate 57 is tapered, it is necessary to incline the partition plate 57itself towards the rear side so as to secure a curvature that does notgenerate a stream separation in the return bend section 47. However, inthe embodiment shown in FIG. 9, since the second wall section 58comprised by the partition plate 57 is oriented at substantially a rightangle to the rotation axis 41, problems such as an increase in thedimension in the axial direction, resulting from slanting the partitionplate 57 towards the rear side to secure a curvature that does notproduce a stream separation in the return bend section 47, may beeliminated. Accordingly, it is possible to increase the efficiency ofthe compressor without increasing the dimension of the turbo-typecompressor 12 in the axial direction.

[0090] That is, according to the turbo-type compressor 12 explainedabove, by tapering only one of the pair of wall sections, i.e., eitherthe first wall section 56 or the second wall section 58, whichconstitute the diffuser section 46, the performance thereof can beimproved quite easily by increasing the width dimension b2 of the outletopening 46 b relative to the inlet opening 46 a. Also, because only oneof the wall sections, either the first wall section 56 or the secondwall section 58, needs to be tapered, the performance of the compressor12 can be improved even more simply.

[0091] In particular, in the embodiment shown in FIG. 9, as describedearlier, since the first wall section 56 is tapered, which constitutesthe front side wall section that is more spacious as compared with therear side of the impeller 19 that has a downstream side passagecommunicating with the diffuser section 46, the dimension in the axialdirection can be made smaller.

[0092] Moreover, it is obvious that the structures of the diffusersection 46 shown in FIGS. 8 and 9 can be adapted to either of thestructures of the diffuser section 46 shown in FIGS. 4 and 6.

[0093] Further, in the above embodiments, although the diffuser section46 is illustrated using a vaneless type diffuser that has no vanes, thediffuser section 46 used in the present invention may be provided withvanes.

INDUSTRIAL APPLICABILITY

[0094] As explained above, according to the turbo-type compressor andthe refrigeration apparatus provided with the turbo-type compressor ofthe present invention, the following effects may be obtained.

[0095] According to the turbo-type compressor of claim 1, since thewidth dimensions of the openings in the axial direction of the inletside and the outlet side are made so that the outlet side is largerrelative to the inlet side, the aspect ratio of the inlet side and theoutlet side is made somewhat smaller and the area ratio is made larger,so that the pressure recovery coefficient in the diffuser section can bemade larger. This design enables effective recovery of the dynamicpressure of the compressed fluid output from the impeller into a staticpressure in the diffuser section without making the structure larger ormore complex, and accordingly, a high compression efficiency is realizedin the turbo-type compressor of the present invention.

[0096] According to the turbo-type compressor of claim 2, withoutaltering the area ratio of the inlet opening to the outlet opening inthe diffuser section, the width dimension of the outlet opening is madelarger relative to the width dimension of the inlet opening. That is,because the radius of the outlet opening is reduced by an amountcorresponding to the increase in the width dimension of the outletopening, the outer radius can be made smaller and the cost of thecompressor can be reduced.

[0097] Also, even if the area ratio of the inlet opening to the outletopening is not altered, because the width dimension of the outletopening is made larger relative to that of the inlet opening, the aspectratio is reduced, the pressure recovery coefficient is made larger so asto reliably improve the performance.

[0098] According to the turbo-type compressor of claim 3, by taperingthe pair of wall sections forming the diffuser section, the performanceof the compressor is readily improved by enlarging the width dimensionof the outlet opening relative to that of the inlet opening. Also,because the wall sections are tapered, it is possible to eliminate aproblem of stream separation in the diffuser section of the refrigerantoutput from the impeller.

[0099] According to the turbo-type compressor of claim 4, by making onlyone of the wall sections that constitute the diffuser section, into atapered shape, the performance of the compressor can be improved quitereadily by increasing the width dimension of the outlet opening relativeto the inlet opening. Also, because only one of the wall sections needsto be made into a tapered shape, the performance can be improved evenmore easily.

[0100] In particular, by tapering the wall section in the front sidewhich has more space as compared with the rear side of the impellerhaving a downstream side passage that communicates with the diffusersection, the dimension in the axial direction can be made smaller.

[0101] According to the turbo-type compressor of claim 5, because thepressure recovery coefficient is improved in each stage of compressionby respective impellers at the respective diffuser sections serving asfluid paths for the fluid output by the respective impellers, a superiormulti-stage turbo-type compressor of high performance may be provided.

[0102] According to the refrigeration apparatus of claim 6, because ahigh efficiency turbo-type compressor, having a diffuser section thatexhibits high performance and produces a high recovery coefficient, isused as a compressor to compress the refrigerant and to output thecompressed refrigerant to the condenser, the cooling efficiency can beimproved significantly, and accordingly, the refrigeration apparatus canproduce superior cooling performance.

1. A refrigeration apparatus, comprising: a compressor for compressing arefrigerant admitted from an intake opening and discharging therefrigerant from a discharge opening; a condenser for condensing andliquefying the refrigerant and forwarding a resultant liquefiedrefrigerant; a throttling mechanism for reducing the pressure of theliquefied refrigerant; and a vaporizer for cooling an object to becooled by exchanging heat between the object to be cooled and aresultant condensed and pressure-reduced liquefied refrigerant, andevaporating and vaporizing the liquefied refrigerant, wherein thecompressor is a turbo-type compressor comprising: a casing provided withan intake opening and a discharge opening; a rotation shaft operated bya driving mechanism; an impeller provided integrally with the rotationshaft; a diffuser section comprised of a pair of wall sections at outerperipheries of the impeller to serve as a fluid passage for a fluiddriven towards the outer periphery side by the rotation of the impellerso that the fluid is drawn in from the intake opening, by the action ofthe impeller which is rotated together with the rotation shaft anddriven by the driving mechanism, to be compressed and discharged fromthe discharge opening through the diffuser section; wherein the diffusersection is formed in such a way that the width dimension in the axialdirection of an outlet opening located at the outer periphery side ismade larger than the width dimension of an inlet opening for the fluidwhich is driven by the impeller.
 2. A refrigeration apparatus accordingto claim 1, wherein the width dimension of the outlet opening is madelarger than the width dimension of the inlet opening without alteringthe area ratio of the inlet opening to the outlet opening of thediffuser section.
 3. A refrigeration apparatus according to claim 1,wherein the pair of wall sections forming the diffuser section is madein a tapered shape so as to separate gradually from each other from theinlet opening towards the outlet opening.
 4. A refrigeration apparatusaccording to claim 1, wherein one of the pair of wall sections formingthe diffuser section is made into a tapered shape so as to separategradually from the other one of the pair of wall sections from the inletopening towards the outlet opening.
 5. A refrigeration apparatusaccording to claim 1, wherein the turbo-type compressor is a multi-stagecompressor having a plurality of the impellers and compresses the fluidfrom the intake opening sequentially by using, first, an upstream-sideimpeller, and successive impellers afterward.